The present invention relates to a device for successively changing elongated flexible sheets or similar flexible objects from an active position to non-active positions. The device incorporates a drum, relative to which the sheets or similar flexible objects are fixed in a suitable manner. The said drum is rotatable by means of a motor.
Devices for changing posters or similar objects are known in a number of more or less complicated embodiments. The known devices are usually of complicated design and many of them are also difficult and awkward with regard to changing posters for new ones. Apart from high complexity known devices have the disadvantage that they are expensive to make.
Examples of such known devices are evident from, i.a., the Swedish patent specification No. 7303560-2 and the U.S. Pat. No. 4,240,219.
An object of the present invention is to provide a device for changing posters or similar elongated flexible objects which device is simple and inexpensive to manufacture and assemble, which has a simple and reliable function, with which it is easy for a layman to change posters etc: and which above all requires a minimum of maintenance and service.
The above tasks and objects have been solved in accordance with the present invention by means of the device mentioned in the descriptive preamble in that the drum is rotatable in two opposing rotational directions, that the rotational directions of the drum are controlled by means of a suitable timing device in relation to the rotational speed of the motor so that rotation takes place in a first direction for such a long time that the sheet located in the active position becomes wound up onto the drum and that a second sheet, located in the first rotational direction after the first sheet, is carried to a position from which the second sheet is unwound from the drum to the active positions upon rotation of the drum in the other rotational direction, and in that the drum thereafter is rotated in the other rotational direction for such a long time that the second sheet becomes unwound from the drum, and in that the rotation of the drum is subsequently stopped by the suitable timing device during such a long time as is wanted in the active position for the second sheet, and in that the aforesaid timing procedure is repeated after the wanted time in the active position.
A particularly advantageous embodiment of the present invention is if the elongated flexible sheets or the similar flexible objects are fixed, either directly or indirectly, in relation to the preferably round drum at essentially the same mutual distances and if the number of used, elongated flexible sheets or similar flexible objects agree with the number of switching of the said motors rotational direction during rotation of the drum one revolution.